There are several possible Mowers of the "L" 155 versions.
John Deere LA155 garden tractor lawn mower. These stopped being made in 2010 (they started production in 2009, and so enjoyed a run of 2 years on the assembly lines). The JD LA155 is powered by a Briggs and Stratton 2 cylinder, V twin engine. This engine is 0.656 liters (40 cubic inches) in size and produces 22 hp.
1998 - 2001 LT Series
John Deere LT155 Engine: Kohler 1-cyl gasoline
2006-2006 L155c, This series was produced only in 2006.
Briggs & Stratton gasoline, 2-cylinder air-cooled, 724 cc [44.2ci ], 25 hp
Model 445777-0168E Code 021125YC, these are the engine numbers from a 25 hp twin cylinder, B&S.
Notes on these engines from parts supplier ereplacementparts.com:
Briggs and Stratton 445777-0231-E1 Engine: The proper flywheel part number and/or the alternator magnet size will determine the alternator type or output.
This 25 hp engine has 3 different possible alternators, standard circuit, dual circuit, tri-circuit. I would need the exact engine model numbers in order to precisely answer your question. Often mower models have choices for the engine they come with. In this situation the engine model is more important than the model of the mower.
Testing an alternator is fairly simple; all you need is a multimeter for testing.
- Disconnect connector from stator.
- Set multimeter for AC volts.
- Attach RED test lead to either pin on stator side of stator connector. (On single wire leads, attach RED test lead to the single pin.)
- On two wire lead models, attach Black test lead to the other pin. On single wire stator connectors attach the Black test lead to the engine ground.
- Prepare the lawn tractor for engine start (set parking brake, blade off, etc). Start engine and run at full throttle.
- Check output. Output for engines of this general size run in the 30 to 50 volt range. For instance the B&S V twin 22 hp AC output at full throttle is 30 Volts minimum. Other B&S on these machines spec 40 Volt minimum.
If your voltages are not in the manufacturers range, or non-existent, your stator is partly shorted or completely burnt out (open circuit). Either way you have to replace it.
A. In the picture is a single lead stator connector.
B. In the picture is a two wire stator connector.